Question

A 300mL solution was made by dissolving 5.0g of MgCl2 in water. What is its molarity?

Answer 1

mols MgCl2 = grams/molar mass
Then M = mols/L solution

Answer 2

300ml solution equals to 0.5 g mgcl2
1ml " " "0.5/300 "
1000ml " " " (0.5*1000)/300g "

1.667M (ans.)

Answer 3

What you have posted is pure blarney.
First error: 300 mL solution equals 5 g MgCl2 and not 0.5. The problem says 300 mL solution and 5.0 g MgCl2.
Second error: you are trying to base molarity on solution/grams and it should be mols/L solution.
The correct solution is as follows:
300 mL contains 5.0 MgCl2 (molar mass 95.2).
mols MgCl2 = 5.0/95.2 = approx 0.0525
M = mols/L = 0.0525/0.300 = 0.175M

Answer 4

i'm sorry. I didn't understand the question properly. Thank u for showing my mistakes.